Doctors warned following codeine overhaul

Doctors have been warned to watch out for codeine-dependent patients following the introduction of prescription-only codeine drugs earlier this month.

Identifying codeine-dependent patients may be difficult, but a study released on Monday says it's vital doctors pick up signs of addiction to prevent serious health complications, which could be fatal.

The study's release comes after products containing codeine, such as Panadeine, Nurofen Plus and Mersyndol, became prescription-only on February 1.

Dr Suzanne Nielsen, lead author of the study published in the Medical Journal of Australia, says doctors need to ask the right questions early, and often, because "it's generally a very hidden problem".

"We don't see any difference between things like age, gender and unemployment," says the senior researcher at the National Drug and Alcohol Research Centre at the University of New South Wales.

"It's definitely more nuanced and some of the stigmatising images for people who commit substance abuse are not helpful for anyone and certainly not helpful for working out anyone with a codeine dependence."

The research, which used data from 41 publications, showed clinical identification of dependence was often delayed and the prevalence of mental health conditions alongside codeine-dependence was very high.

Tolerance to the drug can develop quickly and the harms outweigh the benefits when used in low doses with drugs such as paracetamol and ibuprofen painkillers - which are not made significantly more effective by the addition of codeine, according to the study.

Doctors must build rapport with patients and ask detailed questions about their pain problems, the amount of codeine that's been used and for how long, Dr Nielson said.

"It's not something that might be evident immediately. Often (serious) cases have been identified historically when people have been submitted to hospital with organ damage," Dr Nielson told AAP.

Detoxification and medication based treatments were among a number of options available for those with codeine addictions, but removing the stigma was the first step for people reluctant to come forward and seek help, Dr Nielson said.

"This isn't the fault of the patients, it's the fault of an imperfect medication," the researcher told AAP.